A thermoset material (e.g., a resin in a soft solid or viscous state) changes irreversibly into an infusible, insoluble polymer network by curing. In contrast to a thermoplastic resin that has a constant viscosity at a particular temperature, a thermoset resin has a viscosity that varies as a function of temperature and reaction state (e.g., a degree of resin cross-linking) To illustrate, as a thermoset resin cures, the viscosity may initially decrease (provided that the curing is done at an elevated temperature) and then begin to rapidly increase as the thermoset resin begins to gel.
A printed circuit board (PCB) laminate design may include a multiple-layer “stack-up” design that includes multiple layers. For example, a PCB may be formed of a fiberglass cloth pre-impregnated with a thermoset resin, also referred to as a “prepreg” material. Due to the complex nature of fluid flow properties for thermoset resins, design of PCB lamination processes that use thermoset resins can be challenging.